If it relates to a drug. If it's another type of treatment - "Stosowanie u...". I assume "osoby badane" is a term required by the client, in the clinical study context it's usually "uczestnik" or "pacjent". I'd omit "thus" in Polish altogether, it's not necessary in this medical context, but if it has to be included in translation, I'd say "Stosowanie u osób badanych następująco: pomiar początkowy i badanie kontrolne".